Me and my housemates found a place in the September before term began. Try not to panic too much, or put stress on your friends, as - if not handled properly - the whole househunting process can put a lot of stress on friendships and social stuff.
And, at the end of the day, it doesn't really matter who you live with, as long as you've got a place where you feel comfortable. In the second and third years, it's a lot more about hanging out round other peoples houses, or going down the pub.
The year in halls is a bit of a one-off.